1. Field of the Invention
The present invention relates to a communication system for implementing movement of a session in communication between communication nodes, a communication controlling method in the communication system, a communication node and a communication mediator node constituting the communication system, a communication mediating program executed by a computer in the communication mediator node, and a session moving program executed by a computer in the communication node and a session moving method.
2. Related Background Art
Among the conventional communication methods of TCP/IP and others, there existed no standard method of moving a session in communication from one communication node to another communication node. Therefore, movement of a session in communication was individually handled in such a way that an application explicitly disconnected the session in communication and then reconnected the session in another communication node. In addition, mechanisms of moving the session were dependent upon respective applications, and thus there existed no common platform. Accordingly, there were strong desires for construction of a common platform for moving a communication session.
In order to facilitate the construction of the common platform, it is necessary to provide a standard method for moving a communication session between communication nodes without special awareness of a communication correspondent and to provide a network with a mechanism capable of facilitating the movement of the communication session without any change in the specifications of the communication correspondent.
The above mechanism requires the following three elements. Namely, the three elements are {circle around (1)} a mechanism for ensuring reachability of data (a mechanism of, after a communication correspondent of a certain communication session sends data, delivering the data to a node of a destination to which the communication session has moved), {circle around (2)} a mechanism for ensuring continuity of the session (a mechanism of, in order to continue the session at the destination as well, on the occasion of movement of the session, copying an interior state on the way of the session in communication, into the destination node and restoring the interior state on the way of the session in the destination node), and {circle around (3)} a mechanism for ensuring continuity of a process (a mechanism of copying an interior state of an application process in communication, into the destination node and restoring the interior state of the process in the destination node).
The element {circle around (1)} (the mechanism for ensuring reachability of data) among these elements is such a mechanism that, while a communication session is established between one communication node and a communication correspondent, even if one end of the communication session moves from one communication node to another communication node, the communication correspondent is allowed to send data to the one communication node and the data thereafter can be surely delivered to the other communication node as a destination of the communication session, and it can be said as an indispensable and important element.
The present invention has been accomplished with focus on the above element {circle around (1)}, and an object of the present invention is to provide a communication system, a communication controlling method, a communication node, a communication mediator node, a communication. mediating program, a session moving method, and a session moving program capable of ensuring the reachability of data even with movement of a communication session between communication nodes.